Do email verifiers charge for unknown results?
Most do not. Of 13 verifiers whose billing rules could be read on their own sites in September 2026, 8 state that unknown results are free. Every vendor that states a catch-all rule charges for catch-all results. On expiry, Kickbox and Hunter credits last 12 months, while most other vendors say their pay-as-you-go credits never expire.
The short version
- 8 of 13 vendors with a readable billing rule say unknown results cost nothing, including ZeroBounce, Kickbox, Emailable, Bouncer and Reoon.
- Every vendor that states a catch-all rule bills it. MillionVerifier charges only when its catch-all pass reaches a verdict.
- Kickbox credits expire one year from purchase and Hunter's last 12 months. Most other vendors say pay-as-you-go credits never expire.
- ZapBounce never bills an unknown or a duplicate, bills a catch-all once, and its credits never expire.
Where these numbers come from
- Each rule was read on the vendor's own pricing page, terms or documentation on 2026-09-24. The source for every vendor is listed at the foot of this page.
- A rule counts only if the vendor states it. Where a page says nothing, the table says "Not stated" rather than guessing from a review site.
- NeverBounce, MyEmailVerifier and BriteVerify show no readable billing page to a normal fetch, so no rule is recorded for them.
- ZapBounce's rules are the ones on its pricing page and in the API docs.
Who charges for unknown and catch-all results
An unknown result means the receiving server gave no firm answer. It might have timed out, or blocked the probe. Charging for it means paying for a check that told you nothing.
A catch-all result is different. The verifier did learn something: the domain accepts every address, so no single mailbox can be confirmed. That's why vendors who state a rule all charge for it, and why a few sell a second, deeper pass at extra cost.
| Vendor | Unknown results | Catch-all results |
|---|---|---|
| ZapBounce | Never billed | Billed once |
| ZeroBounce | Free | Billed |
| Kickbox | Not counted against your balance | Billed (as Risky) |
| Emailable | Refunded, with duplicates | Billed (as Risky) |
| Clearout | Returned automatically | Billed |
| Bouncer | Never charged, nor duplicates | Not stated |
| MillionVerifier | Not charged | 1 credit only when resolved |
| Reoon | Refunded automatically | Flagged |
| Hunter | No credit counted | Not stated |
| DeBounce | Not stated | Separate product at 10 credits each |
| Truelist | Not stated | 1 credit, plus 3 for an enhanced pass |
| Scrubby | Not stated | 1 credit quick, 3 credits deep |
| BounceBan | Not stated | 1 credit for every result |
| Verifalia, EmailListVerify, emailverify.io, QuickEmailVerification | Not stated | Not stated |
| NeverBounce, MyEmailVerifier, BriteVerify | Page not readable | Page not readable |
Read on each vendor's own site on 2026-09-24. Wording is the vendor's where quoted. Rules change, so confirm on the vendor's pricing page before you buy.
Whose credits expire, and after how long
Most verifiers now say their pay-as-you-go credits never expire. The exceptions are the ones to watch if you buy a large pack and use it slowly.
Kickbox's terms say credits "automatically expire one (1) year from the date of purchase". Hunter's credits can be used for 12 months. Two vendors add a twist in the small print. Clearout's terms limit idle discounted credits to one year. emailverify.io's pricing page says never, while its FAQ says 12 months.
| Vendor | Credit expiry | Read |
|---|---|---|
| ZapBounce | Never expire; plan credits roll over while the plan is active | Own terms |
| Kickbox | One year from purchase | 2026-09-24 |
| Hunter | Usable for 12 months | 2026-09-24 |
| Bouncer | Never expire | 2026-09-24 |
| Emailable | Never expire; subscription credits roll over | 2026-09-24 |
| MillionVerifier | "No expiry" | 2026-09-24 |
| DeBounce, Reoon, EmailListVerify, Truelist | Never expire | 2026-09-24 |
| Scrubby, BounceBan | Never expire (pay-as-you-go) | 2026-09-24 |
| Verifalia, QuickEmailVerification | Purchased packs never expire | 2026-09-24 |
| Clearout | Never expire; terms cap idle discounted credits at one year | 2026-09-24 |
| emailverify.io | Pricing page: never. FAQ: 12 months | 2026-09-24 |
| ZeroBounce | Subscription credits roll over while active; pay-as-you-go not stated | 2026-09-24 |
Read on each vendor's own pricing page or terms on 2026-09-24. Daily free credits at Verifalia and QuickEmailVerification reset each day and are not counted here.
What these rules do to the price you actually pay
Say you verify 10,000 addresses and 500 come back unknown. At a vendor that bills unknowns, you pay for 10,000 checks. At one that doesn't, you pay for 9,500, and the 500 stay in your file with a label.
Expiry works on a longer clock. Say you buy 100,000 credits to get a lower unit price, then clean only 30,000 addresses this year. A 12-month rule turns the rest into a loss. A never-expire rule keeps the discount real.
Catch-all billing is the rule that's easiest to miss. On a B2B list, catch-all domains can be a large share of the file, so the per-check price applies to every one of them. Our answer on whether to keep catch-all addresses covers what to do with them next.
How ZapBounce bills a verification
Every address comes back as valid, invalid, catch_all or unknown. You pay one credit for valid, invalid and catch_all. You pay nothing for unknown, for a duplicate in the same file, or for an error.
A catch-all domain is found with one probe to a random address at the same domain. The result is labelled catch_all and billed once, never folded into valid. Each row of your results file carries a billed flag, so you can check the charge line by line.
Credits never expire. Packs start at $5 for 1,000 checks with no minimum, and you get 100 free checks every month with no card. The ZapBounce pricing page lists every tier.
Five questions to ask any verifier before you buy
Do unknown results cost a credit? Are duplicates in one upload charged twice? What does a catch-all result cost, and is there a second pass at a higher price? When do credits expire, and does a discount change that? Does the results file show which rows were billed?
If the pricing page doesn't answer all five, the terms of service usually do. For the prices behind these rules, see our verifier pricing index.
Sources
Questions people ask
Do email verifiers charge for unknown results?
Most say they do not. Of 13 vendors whose rules could be read in September 2026, 8 state unknowns are free, including ZeroBounce, Kickbox, Emailable, Bouncer and Reoon. ZapBounce never bills an unknown or a duplicate.
Do email verifiers charge for catch-all results?
Yes, every vendor that states a rule charges for a catch-all result. MillionVerifier charges only when its catch-all pass reaches a verdict, and DeBounce sells catch-all validation separately at 10 credits each. ZapBounce bills a catch-all once and labels it catch_all.
Do Kickbox or Hunter credits expire?
Yes. Kickbox's terms say credits expire one year from the date of purchase. Hunter's credits can be used for 12 months. Both rules were read in September 2026. ZapBounce credits never expire.
Which email verifiers have credits that never expire?
Bouncer, Emailable, MillionVerifier, DeBounce, Reoon, EmailListVerify and Truelist all state their credits never expire, read in September 2026. ZapBounce credits never expire either, and plan credits roll over while the plan is active.
Check your own list's coverage
100 free checks a month, no card. Every result comes back as valid, invalid, catch-all or unknown, and unknowns are never billed.